1. Field of the Invention
The present invention relates to percutaneous medical procedures within the breast. More specifically, the present invention relates to a system and process for performing percutaneous biopsy and instrument guidance within the breast under the imaging and guidance of two-dimensional and/or three-dimensional ultrasonography.
2. Description of the Prior Art
Breast cancer poses a serious threat to the lives of Canadian women. According to the American Cancer Society, one in nine North American women will develop mammary carcinoma (American Cancer Society 1992). This figure has increased from one in twenty in 1940 and reflects a steadily increasing incidence of breast cancer over the last few decades. Breast cancer has shown the highest occurrence of all female cancers, and was the second highest cause of cancer death for women in 1990 and 1991 (Amer. Cancer Soc. 1991). For women aged between 35 and 54, breast cancer is the leading cause of death (Beatty 1992). In 1994, an estimated 17,000 breast cancers were detected in Canadian women, and 5,400 Canadian women died of this disease (NCIC 1994).
Historically, breast disease has been detected and diagnosed using x-ray mammography. Mammography is not only widely available and relatively inexpensive, it has also generally been regarded to be the most sensitive single test available for breast cancer, with a detection rate of 90-95 percent (Frankl 1988, Castor, 1987, Moskowitz 1983, Baker 1982). Early detection and diagnosis have been shown to improve both the morbidity and mortality rates from breast cancer (Shapiro 1982, Morrison 1989, Tabar 1990). Diagnosis of detected focal abnormalities using mammography is based on morphological features of breast lesions such as boundary appearance and distribution of calcifications. Although some lesions can be specifically characterized in this way as either benign or malignant, a large number are radiographically indeterminate. In a large study (Frankl 1988), mammography yielded a false positive rate of 48 percent, and is reported to be even less accurate in characterizing the dense breast tissue of younger women or tissue with fibro cystic disease (Ashley 1989; Robbins 1973). In screening situations, the false positive rate for x-ray mammography may be as high as 75-90 percent (Holmberg 1987). However, a number of large trials have shown that the positive predictive value for non-palpable breast cancer detected by mammography is disappointing. These trials reported that only 20-30% of non-palpable radiographically suspicious lesions are proven to be carcinoma by biopsy (Ciatto 1987, Hall 1988, Homer 1984, Meyer 1984, Rosenberg 1987, Holmberg 1987). In addition, many patients undergo prolonged follow-up with repeated mammograms and ultrasound for benign lesions. This was demonstrated in a large study, in which about 11% of the 34,282 women followed had lesions which were found to be benign. Clearly, mammography has a high rate of false positive diagnoses, leading to unnecessary biopsies, unnecessary careful follow-up of many patients over periods usually 2 year or more, undue psychological stress, inefficient patient management, and increased health care costs.
Improvements in the specificity of diagnosis (i.e. reduction in the false positive rate) would result in fewer unnecessary surgical biopsies performed, lower health care costs and better patient management. Development of noninvasive methods to further characterize indeterminate lesions demonstrated on mammography is therefore highly desirable. Adjunct imaging modalities have been shown to provide additional morphological and physiological information which cannot be obtained by mammography. Characterization of lesions using mammography in conjunction with ultrasound, for example, has been shown to be more accurate than diagnosis by mammography alone. This has particular application for women with dense breasts, where mammography has demonstrated a high rate of inaccuracy.
Therefore, there has been a long standing need to develop a percutaneous method of diagnosing breast diseases and which further allows for the treatment of the diseases to be performed percutaneously. Accordingly, the present inventors have determined that by employing three-dimensional ultrasonography in combination with two-dimensional imaging, breast lesions can be viewed in an entirely novel manner. The present invention preferably employs a three-dimensional imaging system as disclosed in U.S. Pat. No. 5,454,371 and U.S. patent application Ser. No. 08/562,590, filed Nov. 24, 1995, the contents of which are herein incorporated by reference. However, as will be understood by those of skill in the art, other three-dimensional ultrasonographic systems may be employed with the system and method of the present invention with similar success.
Further to this end, the majority of breast lesions operated on typically result in a scar and significant deformity to the patient. While some percutaneous biopsy techniques are presently in use, they are generally time consuming and tedious. It is believed that the system and method of the present invention will be quicker, provide greater accuracy and be significantly less damaging over conventional methods. Features of the present system include percutaneous access to lesions, rapid speed of performing the procedure, continuous feed-back relating to any complication that may occur, and increased flexibility in different approaches to be made to breast lesions.